Negative-pressure cavitation extraction of cajaninstilbene acid and pinostrobin from pigeon pea [Cajanus cajan (L.) Millsp.] leaves and evaluation of antioxidant activity

In this study, an efficient negative-pressure cavitation extraction (NPCE) technique was developed to extract cajaninstilbene acid (CSA) and pinostrobin (PI) from pigeon pea [Cajanus cajan (L.) Millsp.] leaves. The operating parameters were optimised using single-factor experiment and central composite design combined with response surface methodology. Well-fitting models for the extraction of CSA and PI were successfully established. From the economic perspective, the selected operating parameters were: extraction pressure −0.075 MPa, extraction temperature 45 °C, material size 40 mesh, ethanol concentration 80%, extraction time 30 min, liquid/solid ratio 30:1 and 4 extraction cycles. After method development, the extraction yields of CSA and PI using NPCE (5.675 ± 0.127 and 0.538 ± 0.014 mg/g, respectively) were compared with those of the well-known ultrasound-assisted extraction (UAE) (5.594 ± 0.084 and 0.529 ± 0.010 mg/g, respectively). Furthermore, the antioxidant activities of resulting extracts of NPCE and UAE were 0.300, 0.325 mg/mL (IC50) and 1.095, 1.073 mmol/g (TEAC value), according to the DPPH and ABTS+ radical-scavenging assay, respectively. Those results demonstrated that NPCE was comparable to UAE in term of extraction yields and antioxidant activity of extracts. This novel extraction technique also possesses the advantages of low equipment expenditure and capability of high throughput. The results of the present study may provide valuable data for process design and pilot-scale as well as industrial scale-up applications.

► CSA and PI present striking pharmacological activities.
► NPCE possesses the advantages of low expenditure and capability of high throughput.
► A response surface model was established to describe the influence of the studied parameters.
► It was proved that the NPCE process was scalable by pilot-scale application.
► The results may provide valuable data for pilot-scale and industrial applications.